碩士 / 國立臺灣海洋大學 / 海洋生物研究所 / 105 / Halophytophthora is an oomycetous genus and predominantly inhabits mangrove environment. Halophytophthora species mainly are saprobic but their spores can be food for other organisms in the mangrove food web, thus serving as secondary producers. A previous study has shown the production of polyunsaturated fatty acids in mycelia of Halophytophthora, especially eicosapentaenoic acid (EPA, 22:5 (n=3)) and arachidonic acid (ARA, 20:4 (n=6)). Fatty acids with double bonds in the fatty acid carbon chain are called polyunsaturated fatty acids (PUFAs). With the differences in the length of the carbon chain and the position of the double bonds, these fatty acids correspond to different PUFAs,e.g. docosahexaenoic acid (DHA, 22:6 (n=3)), EPA and ARA. These fatty acids have been reported to have beneficial health effects on human including loweringblood pressure, preventing cardiovascular disease and reducing inflammation. Traditionally, PUFAs can be consumed through marine fish but overfishing in recent years has prompted discovery of alternative sources of PUFAs.
In this study, diversity of Halophytophthora in five different mangroves of Taiwan and their fatty acid profile were studied. A total of 14 isolates representing 5 different species were collected based on identification through morphology and sequence analysis of the nuclear 18S and internal transcribed spacers (ITS) rDNA, including H. avicenniae, H. batemanensis, H. exoprolifera, H. polymorphica and H. spinosa var. spinosa. Liquid fermentation of the 14 isolates of Halophytophthora in glucose/yeast extract/peptone broth was used to analyse the fatty acid composition of mycelia; ARA in total fatty acids ranged between 4.16%-29.94% while EPA ranged between 0%-14.16%. No EPA was detected in all isolates of H. spinosa var. spinosa, suggesting that they may lack specific enzymes to transform ARA to EPA. Phylogenetic analysis of the 18S and ITS rRNA gene showed that majority of the Halophytophthora sequences generated in this study and those from the GenBank constitute the Halophytophthora sensu stricto clade with the type species H. vesicula. However, H. spinosa var. spinosa is distantly related with the Halophytophthora sensu stricto clade and other genera in the Pythiaceae. This observation corroborates the result of the fatty acid analysis; Halophytophthora sensu stricto clade produced ARA and EPA while no EPA was produced by H. spinosa var. spinosa.
| Identifer | oai:union.ndltd.org:TW/105NTOU5270001 |
| Date | January 2017 |
| Creators | Ju, Wen-Ting, 朱文廷 |
| Contributors | Pang, Ka Lai, 彭家禮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 62 |
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